The web is full of inferred circuits for the ubiquitous flip flap flower, but I haven't been able to find an actual one, so I burned off the ominous black blob that supposedly hides the 'brain' of the oscillating solar circuit, and am still no wiser. I was expecting an arrangement of semiconductors, diodes, transistors or something under the blob, but all I see is a copper pattern bonded directly to the PCB without any obvious semiconductor material (unless the epoxy black blob is a semi?). I’m fairly sure I didn’t destroy anything during the burn off because I scraped one off as well and got the same pattern. Can anyone figure it out?

I would guess this is a periodically energised electromagnet (solenoid), we used to have a similar this in our shop window when I was a kid it was a pendulum that just ticked back and forth with a solenoid pulling on a magnet on every cycle, in those days it was just a couple of contacts that where linked to the pendulum, no electronics at all.

I would think you burned off the electronics under the black blob.
The circuit would be a relaxation oscillator.

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Thanks Mr Chips. That would seem the logical explanation, but I looked very closely at the residue and saw nothing that resembled anything vaguely electronic. Ditto for the scraped off version (I chiselled it off layer by layer with a jeweller's screwdriver). Can you suggest what solvent might dissolve the blob? I have tried turpentine and acetone to no avail. Chloroform might work but it's nearly impossible to obtain these days.

I have tried turpentine and acetone to no avail. Chloroform might work but it's nearly impossible to obtain these days.

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We've had long discussions about what is required to remove modern potting materials, and it comes down to, "You gotta be nuts". (Sorry, Martinez) Do you have weeks to go out of the country to get banned solvents and give them days to soften the crud? Does it really matter that much to you? These circuits were obfuscated for a reason...to make it too difficult for you to copy them. As far as I'm concerned, it works.

We've had long discussions about what is required to remove modern potting materials, and it comes down to, "You gotta be nuts". (Sorry, Martinez) Do you have weeks to go out of the country to get banned solvents and give them days to soften the crud? Does it really matter that much to you? These circuits were obfuscated for a reason...to make it too difficult for you to copy them. As far as I'm concerned, it works.

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Yes, and life is much easier if you just look at what the circuit does, and make one that does the same from the ground up. No reason to duplicate it exactly. There are many ways to skin a cat - not that I've ever skinned one.

Thanks Allen,
I get a steady 2.1 volts in bright sunshine. It's a good idea to hack an old clock, but given a flip flap costs about $2.50 landed in Perth from China, it hardly seems worth doing except for the intellectual exercise. The PBC I brutalised was from a flip flap that failed after my garden sprinklers drowned it. I opened it up and became intrigued to understand what was under the black epoxy blob. I think MrChips is right about its being a simple relaxation oscillator but the absence of semiconductor material puzzles me. When the new ones arrive, I'll run some tests on one while it's working to see if I can grasp what is casing the cap to discharge and nudge the coil.

I have a friend now living in Perth. He told me that the lead guitarist Hank Marvin, of the Shadows, was also staying there in Perth.

Allen

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Well, well...I never. Just Googled him and Wikipedia says: "Since 1986, Marvin has lived in Perth, Western Australia. He has made impromptu appearances on stage when musician friends visit the area, such as in February 2013 when Cliff Richard held a concert at Sandalford Winery." I had no idea. Quite a nostalgia trip reading about him.

My first post: hi all. If you put a hearing aid ( yes I have 2) next to the flower the phone coil input is 45 pulses per minute. The clever bit is that the mechanical natural frequency is 90 beats per minute for the flapping. So you can adjust the mechanical resonance by putting a little BluTack on the flower head and when the frequency disagrees too much, the response is chaotic, or at any rate, much more interesting to watch.
I go with GopherT. Hit it with 0.75Hz, doesn't matter where from.

@Joey Godalla
If there were no silicon parts inside, then it was likely just a relay oscillator. Frequency seems about right for such a simple device...

You don't have a relay per se, but you do have a solar panel that is moving away from the light and changing voltage (like the relay cutting out) and then springs back to the light and starts charging the cap again. And you do have the coil and capacitor.

...and you have a rather clever manufacturer adding the epoxy to make you think there was magic inside.

Thanks GopherT,
The solar panel is static relative to the circuitry (it doesn't flip flap with the petals), nor is it arranged in a way for a shadow to cause a voltage variation. The only component that moves is the pendulum magnet which is attached to the stem of one of the petals and swings over the coil. Even if it were somehow making use of a reverse current as it swings to cause the capacitor to discharge, it begs the question what is the strange copper pattern under the blob there for.
Incidentally, I think some members have the mistaken the idea that I'm trying to repair this little device. I am not; I am just trying to understand what actually happens "under the blob". I'm still trying.
Thanks again for your suggestions. I'm enjoying the contact with so many brains.

Actually, just looking at the layout again, I wonder if the copper pattern invokes some sort of "field effect" that acts like a spark gap when the cap is fully charged. The closest gap is about .5 millimetre (.02 in), which seems too wide for 6 volts to jump, but the epoxy may have a threshold voltage above which it conducts. Just an idea.

We've had long discussions about what is required to remove modern potting materials, and it comes down to, "You gotta be nuts". (Sorry, Martinez) Do you have weeks to go out of the country to get banned solvents and give them days to soften the crud? Does it really matter that much to you? These circuits were obfuscated for a reason...to make it too difficult for you to copy them. As far as I'm concerned, it works.

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Hi #12,
I don't think I'm nuts, but then again do nutty people know they are? Either way, I have deep desire to know how things work, which is why I am drawing on AAC's enormous reservoir of knowledge, brains and experience.
Bet you're glad you're not in Boston right now.

Can anyone remember how the Unijunction Tramsistor oscillator looks? If one device had come away in the potting compound, I think there may be enough components left for an oscillator. Last one I saw was in a Conn electronic organ for the lowest frequencies.

Thanks GopherT, I have seen this several times prior. It shows two different models. The hyperlink shows one with a creepy face on the petal and a different design inside. It has a vertical coil and two magnets and may indeed have an IC chip as claimed in the diagram although the photo doesn't actually show it. The video, however, shows the model I have, which has no IC in the circuit despite most members believing there had to be one under the epoxy blob and I somehow failed to notice it after stripping down two of them. Nevertheless I appreciate your trying to find the solution. I have new ones on order and will non-destructively test one to increase my understanding. Might also try X-raying it if I can convince my dentist to do it.